Eze tells us Iruke completely vanished in early 2018 and cut off all ties with him and their friends, and even more concerning ... he says her family hasn't been able to contact her either.

According to new legal docs ... the court stated there is reason to believe the children have been "taken, detained, and concealed" and have authorized the L.A. County D.A.'s office to investigate and locate Eze's estranged wife and kids.

He's thankful to have this assistance, and tells us Linda's family -- especially her mother -- have been vital in convincing the court to take action.

Chikezie also has an emotional message for his son -- on his birthday -- and urges anyone who knows about his family's whereabouts to contact the D.A.'s child abduction unit.